41 Anatomy is the study of the structure of an organism. Physiology is the study of the functions an organism performs. The distinction blurs when we apply.
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41• Anatomy is the study of the structure of an organism.
• Physiology is the study of the functions an organism performs.
• The distinction blurs when we apply the structure-function theme, and “anatomy-and-physiology” rolls off the tongue as though it were one big compound noun. The form-function principle is just another extension of
• Epithelial tissues have distinct inner and outer surfaces.
• The outer surfaces are the apical ends of the epithelial cells. They face the air (skin, lungs) or a fluid-filled organ cavity (the lumen of the gut).
• Apical ends may have cilia or be highly folded to increase surface area.
• The inner surfaces are the basal ends; they rest on an extracellular matrix called a basal lamina.
• Some epithelial tissue, such as skin, gets much wear and tear, and thus has a high rate of cell division and replacement.
41• Connective tissue consists of cells embedded in an
extracellular matrix that they secrete.
• Connective tissue functions mainly to bind and support other tissues. Connective tissues have a sparse population of cells
scattered through an extracellular matrix. The matrix generally consists of a web of protein fibers
embedding in a uniform foundation that may be liquid, jellylike, or solid.
• Adipose tissue is a specialized form of loose connective tissues that store fat in adipose cells distributed throughout the matrix. Adipose tissue pads and insulates the body and stores
fuel as fat molecules. Each adipose cell contains a large fat droplet that
swells when fat is stored and shrinks when the body uses fat as fuel.
41• Cartilage has an abundance of collagenous fibers
embedded in a rubbery matrix made of a substance called chondroitin sulfate, a protein-carbohydrate complex. Chondrocytes secrete collagen and chondroitin sulfate. The composite of collagenous fibers and chondroitin
sulfate makes cartilage a strong yet somewhat flexible support material.
The skeleton of a shark is made of cartilage and the embryonic skeletons of many vertebrates are cartilaginous.
We retain cartilage as flexible supports in certain locations, such as the nose, ears, and vertebral disks.
• Nervous tissue is composed of neurons and glial cells.
• Neurons are extremely diverse in size and form. They function by generating electrochemical signals in the form of nerve impulses.
• These impulses are conducted via long extensions to other parts of the body where they communicate with other neurons, muscle cells, or secretory cells to control activities of organ systems.
• Glial cells provide a number of support functions for neurons.
41The neuron consists of a cell body and two or more extensions, called dendrites and axons.
Dendrites transmit nerve impulses from their tips toward the rest of the neuron.
Axons transmit impulses toward another neuron or toward an effector, such as a muscle cell.
41• Smooth muscle, which lacks striations, is found in the
walls of the digestive tract, urinary bladder, arteries, and other internal organs. The cells are spindle-shaped. They contract more slowly than skeletal muscles but
can remain contracted longer. Controlled by different kinds of nerves than those
controlling skeletal muscles, smooth muscles are responsible for involuntary body activities. These include churning of the stomach and
41• The efforts of all systems must be coordinated for the
animal to survive. For instance, nutrients absorbed from the digestive
tract are distributed throughout the body by the circulatory system.
The heart that pumps blood through the circulatory system depends on nutrients absorbed by the digestive tract and also on oxygen obtained from the air or water by the respiratory system.
• Any organism, whether single-celled or an assembly of organ systems, is a coordinated living whole greater than the sum of its parts.
• Homeostasis depends on the ability to regulate the functions of organs and organ systems.
• Generally, the regulatory systems are the nervous system and the endocrine system.
• Maintenance of homeostasis is dependent on information received, specifically feedback information that signals any discrepancy between the set point (the particular desired condition or level) and the conditions present.
• The difference between the set point and the feedback information is the error signal.
41 Physiological Regulation and Homeostasis
• Cells, tissues, and organs are effectors that respond to commands from regulatory systems. Effectors are controlled systems.
• Regulatory systems obtain, process, and integrate information, then issue commands to controlled systems, which effect change.
• Regulatory systems receive information as negative feedback, which causes effectors to reduce or reverse a process; or positive feedback which tells a regulatory system to amplify a response.